Foreign matter adhering to surfaces during manufacture of, for example, semiconductor wafers, media for hard disk drives (HDD), media substrates, and the like is a cause of manufacturing defects. Accordingly, it is absolutely necessary to inspect the surface thereof to determine whether or not the product is acceptable, and to elucidate the cause when defects occur.
In order to perform such inspections at high speed, a commonly conducted procedure is to irradiate the surface of an inspection subject with light of a laser or the like, receive the scattered light or diffracted light, and conduct arithmetic processing with respect to the intensity of the received light signals (see Patent Documents 1-3).
Specifically, the following Patent Document 1 discloses a surface inspection apparatus which concentrically scans the surface of a rotating wafer while scanning the surface of the wafer with laser light, and which detects the scattered light of laser light stemming from foreign matter and the like adhering to the surface of this wafer (see FIG. 1).
On the other hand, the following Patent Document 2 discloses a method in which the surface of an inspection subject is irradiated with a laser beam, and the light reflected from the irradiated region on the inspection subject irradiated by this laser beam is obliquely received by multiple light-receiving units at different incident light angles with respect to the surface of the inspection subject. With this method, adhering condition of the foreign matter on the inspection subject is determined based on the proportions of the amounts of light received by the respective light-receiving units (see FIG. 1). In addition, this Patent Document 2 states that the incident light angles during this process are approximately 2° to 30°.
On the other hand, Patent Document 3 discloses that the presence or absence of surface defects of an inspection subject is detected from the intensity of reflected light when the surface of the inspection subject is obliquely irradiated with laser light, and that protrusions or recesses in the surface of the inspection subject are detected from interference fringes of the reflected light.
However, according to the aforementioned conventional surface inspection methods, although it is possible to perform high-speed detection of the presence or absence of a foreign matter on the surface of an inspection subject, it has been impossible to determine how the foreign matter adheres to the surface of the inspection subject.
For example, in the case where foreign matter only lightly adheres to the surface of a wafer, it would be possible to remove the foreign matter by rewashing the wafer. On the other hand, in the case where foreign matter adheres to the surface of a wafer with an intermediate degree of strength, the foreign matter could be removed by wiping the surface of the wafer. Furthermore, in the case where foreign matter strongly adheres to the surface of a wafer, the foreign matter could be removed by repolishing the surface of the wafer.
However, with the aforementioned conventional surface inspection methods, it is difficult to suitably perform aftertreatment following inspection, because it is impossible to determine with what degree of strength the foreign matter adheres to the surface of an inspection subject.
Patent Document 1: Japanese Unexamined Patent Application, First Publication No. H06-082376
Patent Document 2: Japanese Unexamined Patent Application, First Publication No. H10-221270
Patent Document 3: Japanese Unexamined Patent Application, First Publication No. H10-132535